In a TDM/TWDM-PON system, a rogue Optical Network Unit (ONU) refers to the behavior that the ONU does not turn on or turn off a laser in a time slot allocated by an uplink bandwidth or it transmits an uplink signal in a wrong time slot and thereby hinders normal uplink transmission of other ONUs. Among all kinds of rogue behaviors, the long-shining rogue is the most troublesome. A long-shining rogue ONU always keeps its laser in an operating state and transmits a random signal, an idle signal or other unexpected signals all the time. As illustrated in FIG. 1, the long-shining rogue ONU occupies upload time slots allocated to other normal ONUs and thus results in crashing with other uplink signals. Therefore the long-shining rogue ONU can cause all the other well-operating ONUs to fail to transmit the uplink signals and thus may impose a serious impact on the operation of the network.
Currently, to identify a long-shining rogue ONU, a possible solution is to turn off optical transmitter modules of ONUs in the system one by one based on a control command from an Optical Line Terminal (OLT). With this one-by-one detection method, the OLT can finally identify which of the ONUs is a long-shining rogue ONU.
However, since the long-shining rogue ONU is mainly caused by an MAC error or a transceiver failure, the above one by one detection method can not identify a long-shining rogue ONU in the following conditions:
1) A long-shining rogue ONU can not respond to a control message of the OLT and refuses to shut down its optical transmitter.
2) A long-shining rogue ONU can respond to a control message of the LT but can not perform the control command to shut down its transmitter due to hardware malfunction or other failures.
In these cases, it is necessary to identify a long-shining rogue ONU manually, which may result in a huge maintenance cost. Therefore, it is vital for a network operator to identify which of the ONUs is a long-shining rogue ONU when the PON system fails. Especially in a practical implementation, there has been no effective solution to remotely and automatically identifying a long-shining rogue ONU which does not respond.